This invention relates to electron beam exposure apparatus, and particularly to an electron beam exposure apparatus for forming a predetermined pattern on a sample with respect to the positions of the reference marks formed on the sample.
In the electron beam exposure apparatus, the sample is scanned by the electron beam to have a predetermined pattern formed. The formation of a pattern is generally performed with respect to the positions of the reference marks which are determined by scanning the reference marks by the electron beam.
The positions of the reference marks are often determined by use of secondary electron signals which are obtained from the reference marks when the reference marks are scanned by the electron beam. However, these signals are generally weak and have a S/N ratio reduced with a passage of time.
This problem can be solved by increasing the energy of the electron beam because the secondary electron signal intensity increases as the energy of the electron beam rises. Although the energy of the electron beam is increased by raising the accelerating voltage of electron beam, the increase of the intensity of the reference mark detection signals, in the normal electron beam exposure apparatus, will widen the width of the pattern, thus making high-precision patterning difficult.